The majority of towel and issue products are presently manufactured according to one of either the conventional wet pressing (CWP) or through-air drying (TAD) processes. In the CWP process, water is removed from the nascent web by mechanical pressure and the resulting sheet is dry embossed. A disadvantage of this process is that it densifies the web, decreasing bulk and absorbency in the resultant sheet. The TAD process is frequently preferred for the manufacture of tissue and towel because it avoids the compressive forces of the dewatering step in the CWP method. In the TAD process, the wet web is formed by depositing a papermaking furnish onto a moving forming fabric where it is initially drained, and then transferring the resulting very wet web onto a TAD fabric, which is generally of a very open and permeable design. The TAD fabric is caused to travel around an open drum where the sheet is non-compressively dried by passing hot air through the web while it is held in intimate contact with the fabric. It is well known that fabrics having a three-dimensional (i.e. non-planar) paper side surface can introduce protuberances into the sheet which can, in turn, impart significantly increased bulk and absorbent capacity to the resulting paper product. The present invention is directed towards fabrics of this type.
Fabrics for use in the formation and through-air drying of tissue products to enhance the bulk of those products are well known. See for example WO 2005/035867 to Lafond et al. which discloses a multilayer tissue forming fabric having topographical height differences between at least two top weft yarns. US 2004/0182466 to Johnson et al. discloses a multilayer TAD fabric with two weft and one warp system in which the pattern causes the warp yarns to stand proud of the papermaking surface to impart bulk. U.S. Pat. No. 6,673,202 to Burazin et al. discloses patterning and bulk enhancement in a TAD fabric by applying a polymeric material onto a substrate fabric. U.S. Pat. Nos. 5,853,547 and 5,839,479 both to Wright et al. disclose a single layer TAD fabric woven according to a 7/3 broken twill design to provide open basket-like areas for high bulk and absorbency in the resulting paper product; in this fabric there are 4 small and 3 larger CD yarns under each PS float, the CD yarns having alternating large and small diameters.
U.S. Pat. No. 4,438,788 to Harwood discloses a papermakers fabric having surface floats on both the PS and MS for improved sheet contact area and improved abrasion resistance. The fabric also includes a plurality of stuffer pick receiving sheds defined by warp yarns of non-circular generally rectangular cross section. The amount of stuffer picks used in the fabric will depend on the air permeability desired. A pin seam is created at the opposing fabric ends by symmetrically reweaving the warp yarns into the fabric to create the seaming loops. The fabric includes three layers of weft yarns interwoven with a single system of warp yarns to provide a smooth surface and high degree of contact with the paper sheet to increase drying efficiency. There is no disclosure of the use of this fabric to provide a PS which includes pockets or depressions to enhance the bulk of a paper sheet formed or conveyed thereon.
WO2006/113818 discloses a through air during fabric for producing tissue and related products. The fabric is a single layer fabric that includes pockets on both sides bounded by warp and weft yarns having extended floats. The yarns within the pockets are woven in a plain weave. Three different warp contours for the warp yarns are required, making the fabric more complex to weave and resulting in non-uniformities.